Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$134.90	4.792%	$141.3644	$141.36	$141.35	$141.40
Purchase #2	$67.65	3.711%	$70.1605	$70.16	$70.15	$70.20
Purchase #3	$133.78	7.456%	$143.7546	$143.75	$143.75	$143.80
Purchase #4	$99.65	11.435%	$111.045	$111.05	$111.05	$111.00
Purchase #5	$12.62	6.330%	$13.4188	$13.42	$13.40	$13.40
Purchase #6	$204.83	11.702%	$228.7992	$228.80	$228.80	$228.80
Purchase #7	$7.31	3.396%	$7.5582	$7.56	$7.55	$7.60
7 purchase totals =	$660.74		$716.1007	$716.10	$716.05	$716.20